1. Field of Invention
The invention relates to a manually operated calculating device.
2. Brief Description of Previous Art
An early development of a manually operable calculating device is the abacus which comprises a plurality of transversely spaced vertically disposed strings having movable counters thereon but there is no resulting numerical reading of a calculation.
In teaching simple or elementary arithmetic functions to beginning school graders, it is very helpful to the learning process to reduce mental calculations or the combination of visual and mental calculations, such as a teacher illustrating on a blackboard, to a hands-on situation in which the pupil or school grader applies his hands physically in carrying out the calculations demonstrated by the teacher. Where the pupil can physically carry out the calculating function and observe or see what he is doing, the mental process of absorbing and understanding the calculation process and its result is greatly expedited. This has been attested to by teachers involved in teaching arithmetic to beginning learners.